Because of the force of gravity and the nose-down (diving) turn before impact, the aircraft likely reached a higher airspeed at impact than when control was lost. This suggests that the aircraft's airspeed was probably below 58 mph when control was lost. Since the stall speed for this aircraft in the configuration at the time control was lost is about 60 mph, it is concluded that the loss of control was due to an aerodynamic stall. The increased g-loading in the turn, the reduction in power, the heavy weight of the aircraft, its aft C of G condition, and the retraction of the flaps would have contributed to reduced climb performance. Because of the wind conditions, the aircraft's airspeed may have been changing rapidly up and down. As well, the pilot's attempt to maintain a climb in the left turn out of wind would have caused the aircraft's airspeed to decrease. The airspeed likely decreased below the flaps-up stall speed during the left turn, and the left wing stalled. The aft C of G condition would have contributed to the adverse characteristics of roll, yaw, and pitch that followed the stall. The pilot's initial response, inputting right aileron, likely aggravated the stall. His attempt to reach the bay in the lake by turning into the left bank and pushing the flight control forward may have allowed the aircraft to start flying again; however, the aircraft's height above the lake was too low to allow the aircraft to reach level flight before striking the surface. It is not known why the two passengers could not exit the aircraft. The centre seat, once it broke loose, may have injured and incapacitated the passengers or impeded their escape.Analysis Because of the force of gravity and the nose-down (diving) turn before impact, the aircraft likely reached a higher airspeed at impact than when control was lost. This suggests that the aircraft's airspeed was probably below 58 mph when control was lost. Since the stall speed for this aircraft in the configuration at the time control was lost is about 60 mph, it is concluded that the loss of control was due to an aerodynamic stall. The increased g-loading in the turn, the reduction in power, the heavy weight of the aircraft, its aft C of G condition, and the retraction of the flaps would have contributed to reduced climb performance. Because of the wind conditions, the aircraft's airspeed may have been changing rapidly up and down. As well, the pilot's attempt to maintain a climb in the left turn out of wind would have caused the aircraft's airspeed to decrease. The airspeed likely decreased below the flaps-up stall speed during the left turn, and the left wing stalled. The aft C of G condition would have contributed to the adverse characteristics of roll, yaw, and pitch that followed the stall. The pilot's initial response, inputting right aileron, likely aggravated the stall. His attempt to reach the bay in the lake by turning into the left bank and pushing the flight control forward may have allowed the aircraft to start flying again; however, the aircraft's height above the lake was too low to allow the aircraft to reach level flight before striking the surface. It is not known why the two passengers could not exit the aircraft. The centre seat, once it broke loose, may have injured and incapacitated the passengers or impeded their escape. When the pilot entered a turn, the combined effects of the increased g-forces, power reduction, the aircraft's heavy weight, the aft C of G, retraction of the flaps, and the wind conditions resulted in the aircraft stalling. The aircraft struck the lake surface before the pilot was able to re-establish a level-flight attitude. The aircraft was operating in excess of 385 pounds above the maximum gross take-off weight, and the C of G was about 2.7 inches aft of the aft limit. This loading configuration aggravated the stall characteristics of the aircraft. The pilot reduced power and raised the flaps before the climb was complete, contrary to the Pilot Operating Handbook, thereby increasing the aircraft's stall speed.Findings as to Causes and Contributing Factors When the pilot entered a turn, the combined effects of the increased g-forces, power reduction, the aircraft's heavy weight, the aft C of G, retraction of the flaps, and the wind conditions resulted in the aircraft stalling. The aircraft struck the lake surface before the pilot was able to re-establish a level-flight attitude. The aircraft was operating in excess of 385 pounds above the maximum gross take-off weight, and the C of G was about 2.7 inches aft of the aft limit. This loading configuration aggravated the stall characteristics of the aircraft. The pilot reduced power and raised the flaps before the climb was complete, contrary to the Pilot Operating Handbook, thereby increasing the aircraft's stall speed. The shoulder harnesses worn by the pilot and the front passenger likely prevented serious head injuries. The centre seat broke from its footings. This may have incapacitated the two passengers inside the aircraft or impeded their escape. One passenger drowned while trying to reach shore. Life jackets were available in the aircraft but were not used by the pilot or passengers.Other Findings The shoulder harnesses worn by the pilot and the front passenger likely prevented serious head injuries. The centre seat broke from its footings. This may have incapacitated the two passengers inside the aircraft or impeded their escape. One passenger drowned while trying to reach shore. Life jackets were available in the aircraft but were not used by the pilot or passengers.